The present invention relates to a trimming circuit, an electronic circuit, and a trimming control system for an electronic circuit, such as a semiconductor device, for adjusting electrical characteristics of the electronic circuit.
In a semiconductor integrated circuit, a fuse may be used to realize a desired operation setting or a desired adjustment. For example, an electronic circuit, such as a semiconductor device, may use a trimming circuit to adjust the characteristics of the electronic circuit. The trimming circuit changes the resistance through the switch operation of a transistor and includes a fuse circuit for performing such a switching operation. The fuse circuit has a plurality of fuses and controls the switch operation of a trim sense circuit corresponding to each fuse by breaking or not breaking each fuse.
When trimming is executed, “probe trimming” is often performed in the prior art (refer to, for example, Japanese Laid-Open Patent Publication No. 2004-214580). To enable probe trimming, a probe pad is arranged in a trimming circuit. Current is supplied to the probe pad to break a fuse. The breaking of the fuse results in the adjustment of a resistor or other elements connected via a trim sense circuit in a subsequent stage. Probe trimming is advantageous in that it ensures the breaking of a fuse.
However, the characteristics of a semiconductor device may change after packaging. For example, the application of stress to a chip subsequent to molding may result in an assembly shift, which would change the band gap. As a result, the voltage at a reference power supply or the like would change.
To solve this problem, “package trimming”, which is performed after packaging, has recently been developed. As shown in FIG. 2, to enable package trimming, a current supply circuit 30 is connected to a fuse F, which is grounded. An n-type MOS transistor T1, a resistor, and a diode D1 are connected in series in the current supply circuit 30. The n-type MOS transistor T1 is connected to a power supply PS. A gate terminal of the n-type MOS transistor T1 is connected to a selector control circuit 12. The selector control circuit 12 selects the fuse F that is to be broken. The diode D1 is used for electrostatic discharge (ESD) protection and prevents backflow of a current, which would break the fuse F.
The selector control circuit 12 specifies the fuse F that is to be broken and activates the n-type MOS transistor T1 to supply current to the fuse F from the power supply PS. As a result, trimming is performed. Such trimming performed after packaging enables the assembly shift or the like to be readjusted.
In package trimming, a current supply circuit supplies current to a fuse and causes the fuse to break. Thus, package trimming requires current of at least a predetermined value to break the fuse. However, depending on the characteristics of the current supply circuit or the fuse (e.g., depending on variations of the fuse resistor), a sufficient amount of current may not be supplied.
In particular, package trimming has high process dependency. Therefore, package trimming may fail to enable sufficient trimming when package trimming is performed on a device that is manufactured with new processes and includes a current supply circuit or fuses with varying characteristics.